U.S. patent number 6,707,646 [Application Number 09/920,475] was granted by the patent office on 2004-03-16 for method and apparatus for dynamically controlling the flying behavior and height of a read/write head in a storage device by manipulating the spring constant of the suspension.
This patent grant is currently assigned to Hitachi Global Storage Technologies Netherlands B.V.. Invention is credited to Ruediger Friedrich Berger, Andreas Dietzel, Friedrich Fleischmann.
United States Patent |
6,707,646 |
Berger , et al. |
March 16, 2004 |
**Please see images for:
( Certificate of Correction ) ** |
Method and apparatus for dynamically controlling the flying
behavior and height of a read/write head in a storage device by
manipulating the spring constant of the suspension
Abstract
A suspension arm (300) of a disk storage device has an elastic
portion (310) with thickness d.sub.1 and a rigid portion (320) with
thickness d.sub.2. At the free end of the suspension arm, a slider
(325) is mounted on the suspension arm. The bottom surface of the
slider has a distance FH to a top surface of a hard disk (329). The
suspension arm particularly comprises a heating element (330)
disposed on the suspension arm. An electric current I.sub.c flowing
through electrical supply wires (350) causes the temperature of the
suspension arm locally to rise and therefore its spring constant to
decrease. Together with the force F.sub.a resulting from the air
cushion effect of the slider a new equilibrium flying height FH is
stabilized.
Inventors: |
Berger; Ruediger Friedrich
(Heidesheim, DE), Dietzel; Andreas (Wallertheim,
DE), Fleischmann; Friedrich (Erlangen,
DE) |
Assignee: |
Hitachi Global Storage Technologies
Netherlands B.V. (NL)
|
Family
ID: |
8169683 |
Appl.
No.: |
09/920,475 |
Filed: |
August 1, 2001 |
Foreign Application Priority Data
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Aug 29, 2000 [DE] |
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001 18 660 |
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Current U.S.
Class: |
360/294.7;
G9B/21.026; G9B/5.231; G9B/5.153 |
Current CPC
Class: |
G11B
5/6005 (20130101); G11B 5/4833 (20130101); G11B
7/122 (20130101); G11B 21/21 (20130101); G11B
5/607 (20130101); G11B 11/1058 (20130101) |
Current International
Class: |
G11B
5/60 (20060101); G11B 5/48 (20060101); G11B
21/21 (20060101); G11B 11/00 (20060101); G11B
7/12 (20060101); G11B 11/105 (20060101); G11B
005/56 () |
Field of
Search: |
;360/294.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 425 916 |
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May 1991 |
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EP |
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0 605 343 |
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Jun 1994 |
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EP |
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0 886 264 |
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Dec 1998 |
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EP |
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5189906 |
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Jul 1993 |
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JP |
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6084221 |
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Mar 1994 |
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JP |
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08030947 |
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Feb 1996 |
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JP |
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WO 98/27547 |
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Jun 1998 |
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WO |
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Primary Examiner: Heinz; A. J.
Attorney, Agent or Firm: Martin; Robert B. Bracewell &
Patterson, L.L.P.
Claims
What is claimed is:
1. A method of controlling the flying height of a read/write head,
comprising: providing a read/write head mounted on a suspension
arm; suspending the head above a storage media with a spring force
having a spring constant; pushing on the head with the spring force
against an aerodynamic lift force acting upon the head; and varying
the spring constant of at least part of the suspension arm to
adjust the flying height, a roll, and a pitch of the head.
2. The method of claim 1, further comprising the step of varying
the temperature of the suspension arm at least locally with a coil
wrapped around at least a portion of the suspension arm.
3. The method of claim 1, further comprising the step of varying a
magnetic field applied to at least part of the suspension arm.
4. The method of claim 1, further comprising the step of varying an
electric field in at least part of the suspension arm.
5. The method of claim 1, further comprising the step of varying
the spring constant of at least part of the suspension arm to
adjust a twist of the head.
6. A data storage device, comprising: a movable storage medium and
a read/write head placed in proximity to the storage medium at a
flying height and mounted on a suspension arm for flexibly
suspending the head above the storage medium and for pushing on the
head with a spring force against an aerodynamic lift force acting
upon the head; wherein at least part of the suspension arm has a
material with a parameter-dependent spring constant; and means for
controlling the spring constant by said parameter to adjust the
flying height, a roll, and a pitch of the head; and wherein the
parameter is a strength of a magnetic field.
7. The data storage device of claim 6, wherein the means for
controlling the spring constant by said parameter adjusts a twist
of the head.
8. The data storage device of claim 6 wherein at least a bending
part of the suspension arm comprises a bulk material with a
parameter-dependent spring constant.
9. The data storage device of claim 6 wherein at least part of the
suspension arm comprises a layer of a material with a
parameter-dependent spring constant.
10. The data storage device of claim 5 wherein the spring constant
of the material is characterized by an in-homogeneous
distribution.
11. The data storage device of claim 5 wherein the spring constant
of the material is characterized by an elevated sensitivity that
aligns longitudinally or laterally relative to an axis of the
suspension arm.
12. A suspension system for a data storage device, comprising: a
movable storage medium; a read/write head placed in proximity to
the storage medium at a flying height, wherein the head is mounted
on a suspension arm for flexibly suspending the head above the
storage medium, such that the suspension arm pushes the head with a
spring force against an aerodynamic lift force acting upon the
head; wherein at least part of the suspension arm comprises a
material with a parameter-dependent spring constant; magnetic means
for acting upon the material with the parameter to adjust the
flying height, a roll, a pitch, and a twist of the head by a
stretch of a magnetic field; and wherein the material with a
parameter-dependent spring constant forms a layer in the suspension
arm.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
This invention generally relates to rigid or hard disk drives or
tape recording devices which store information or data on rotating
or moving storage media. More specifically, the invention relates
to a method and apparatus for dynamically controlling the flying
behavior of a read/write magnetic head as a rotating magnetic disk
spins under the head or as a moving magnetic tape moves under the
head.
2. Description of the Related Art
Magnetic disk storage devices known in the prior art comprise an
air-bearing slider. The slider itself is mounted on a so-called
suspension arm which essentially functions as a load beam and which
comprises a rigid portion and an elastic portion, wherein the
elastic portion generates a load for urging the slider towards or
away of the recording medium, so that the slider on which an
electromagnetic transducer is mounted is pushed to the recording
medium or pulled away from the recording medium with a certain
necessary load.
For example, when a recording medium such as a magnetic recording
disk is rotating, the load exerted on the slider is balanced by the
airflow of an air cushion force exerted on the air bearing surface
of the slider. As a result, the slider flies above the recording
medium with a very fine gap, the so-called "flying height."
The flying height of a slider carrying a magnetic read/write head
above a rotating magnetic hard disk lies currently in the range of
20 nanometers and will likely decrease in the future. In currently
known hard disk devices the flying height is substantially
determined by the particular design of an air bearing surface of
the slider and a head gimbal assembly. But thereupon variations of
the flying height within a few nanometers may exist for
non-identical devices of the same type owing to fabrication
tolerances. These tolerances considerably influence the writing and
reading characteristics to and from the hard disk.
Two different groups of types of prior art magnetic head suspension
mechanisms are known. In a first group, a thin film formed on the
elastic portion of the suspension arm which is expandable or
shrinkable due to an internal stress of the film itself causes the
elastic portion and thereby the arm to bend thus varying the flying
height of the read/write head above the disk surface. However, the
bending of the suspension arm towards the disk surface increases
the spring force pushing against the aerodynamic lift of the
slider.
Transducers for bending the suspension arm, piezoelectric films, or
bi-metallic strips have been proposed in the art. Approaches
belonging to the first mentioned group are disclosed for instance
in U.S. Pat. No. 5,825,590, "Magnetic Head Suspension Mechanism
with a Thin Film Thereon For Creating a Bent Portion of a Vibration
Absorbing Portion," assigned to Fujitsu Ltd., Japan and in U.S.
Pat. No. 5,377,058, "Fly Height Servo Control of Read/Write Head
Suspension" assigned to IBM Corporation, New York.
Another group of prior art approaches provides for a one-time and
static adjustment of the spring pressure and/or the shape of the
bending of the suspension arm. In Japanese Abstract JP 5189906 A,
during production of floating type magnetic heads, it is therein
proposed to set the floating amount of a slider at a small and
exact amount by transferring heat energy to the spring part of the
suspension arm and adjusting the spring pressure. Applying the heat
is particularly accomplished by irradiating the spring with a laser
beam and setting the bending amount in the rolling direction of the
spring part by a discrete spring pressure regulation. After having
set the bending amount the slider is mounted on the suspension
arm.
According to another static approach disclosed in Japanese Abstract
JP 63281283 A, the spring part is made of a superelastic material
such as a shape-memory alloy which allows that the initial form of
the spring part is rather a bent shape. The initial form is
deformed until it is approximately parallel to the disk surface.
Since only the spring part is made of the super elastic material,
an in-plane rigidity is ensured and in addition the spring constant
is minimized.
The above approaches using a transducer element have the drawback
that such an element requires larger areas on the suspension what,
for instance, complicates further miniaturization of the suspension
arm.
SUMMARY OF THE INVENTION
The concept underlying the present invention is to influence or to
vary the spring constant of a suspension and therefore to influence
the equilibrium state of the prementioned two opposite forces, one
resulting from the aircushion underneath the air-bearing surface of
the slider thus causing a lift or sink force and the other force
provided by the spring force of the suspension itself. By
disturbing this equilibrium state of forces, the flying height of
the read/write head can be changed in a controlled manner. By a
controlled variation of the spring constant, the flying height
therefore can be adjusted very precisely.
In contrast to the prior art approaches described above, the
present invention provides for a passive as well as a active
mechanism where actuation of the read-/write head is accomplished
only by varying the spring constant k, and not by active deflection
DX as in the prior art approaches, F=k-DX. In contrast to the prior
art approaches, where the suspension is deflected actively by
providing a bending force or bending momentum, according to the
present invention the suspension, moreover, is being bent merely as
a consequence of the new equilibrium of the mechanical forces
acting upon the slider. In addition or alternative to the bending,
the suspension can also be bent locally or even buckled by locally
varying the spring constant give by the elastic modulus of the
suspension material, respectively.
This invention therefore enables adjusting of an incorrect gramload
or varying gramload only by (actively) adapting the spring constant
appropriately. This can be accomplished already during the
manufacturing process for the disk storage device after the
suspension together with the read/write head have been assembled to
the storage device or it can be accomplished during HDD operation
as an active adjustment tool.
In addition, the proposed actuation scheme can also be implemented
in a very small area on the suspension thus, for instance, enabling
further miniaturization of the suspension arm.
For measuring the flying height of the head, there exist a number
of methods and systems e.g. a thermal proximity sensing technique
used in scanning probe microscopy sensors and exemplarily disclosed
in U.S. Pat. No. 5,527,110 (Abraham et al.) entitled, "Method and
Apparatus for Detecting Asperities on Magnetic Disks using Thermal
Proximity Imaging". As the spinning velocity of the hard disk is
nearly constant during operation of the disk storage device, the
lift or sink forces are nearly constant too for a given design of
the slider, in particular its shape of the air-bearing surface,
thus allowing a one-time adjustment of an incorrect gramload. In
addition, a particular flying height can be set during the
manufacturing process.
Besides a static adjustment of the spring force by way of varying
the spring constant, also an active or dynamic flying height
adjustment can be accomplished to guarantee a good read and write
characteristic and particularly the operation characteristic of the
underlying spinning storage system.
Thereupon, through the high-speed spinning of the disk, the entire
disk storage device will normally change its temperature during
operation. This does also raise the temperature of the suspension
arm and the air temperature inside a disk storage housing.
Different temperatures of the suspension arm particularly cause
changes of the spring force and thus corresponding changes of the
flying height of the head. Variations of the air pressure or
contamination of the air bearing surface have an impact on the air
streaming underneath the slider and thus influence the lift force
actuating on the slider. All these effects influencing the flying
height can be dynamically adjusted by the present invention.
Thereupon, variations in the speed of rotation of the hard disk and
its influence on the flying height of the read/write head can be
adjusted accordingly, for example in a low and high performance
mode of the HDD.
Further environmental properties can be the degradation of
materials over the time of operation of the hard disk which
therefore has to be corrected to keep the optimum flying height in
order to achieve reliability of the hard disk.
The invention also allows for dynamically setting a particular
flying height so that the read/write head can be kept at a minimum
flying height only during the read/write head is reading or writing
to the magnetic disk. When there is no reading or writing access,
which is about 90% of the hard disk spinning time, the read/write
head can be withdrawn from the minimum flying height in order to
enhance mechanical robustness of the hard disk. Thus, the invention
enables dynamic two- or more-level operation of the read/write
head.
Another technical field for advantageously applying the invention
is future read and write processes which might need for both a
different but defined flying height in order to achieve an ideal
performance such as the storage density. For example, it might be
more convenient to write magnetic bits at very small flying height
while reading of bits is still possible at a higher flying height.
In particular during the seek the servo pattern can be read with
sufficient resolution at higher flying height. This would result in
a decreased seek time. By actively controlling the flying height
this could be realized and would also increase the life-time of the
hard disk.
Changing the flying height thereupon enables to position the
read/write head in a kind of parking position, where it is
protected from damage thus being shock resistive. Additionally,
when the slider is far away from the disk surface, the air friction
force between the slider and the disk surface decreases and thus
decreases, as a consequence, the power consumption which is needed
to spin the hard disk.
Still another advantageous application field of the invention is
use of disk storage devices in portable devices like laptops,
mobile telephones or the like, where it might be useful to reduce
power consumption by reducing the spinning velocity of the hard
disk. Reducing the velocity of rotation of the disk may have an
effect on the air-bearing forces and therefore might result in a
variation of the flying height thus changing the performance of the
device.
The variable suspension spring constant, in a first embodiment, is
realized by varying locally the material temperature of the
suspension arm. Such a temperature variation can be realized by a
small heater deposited onto the suspension arm, for instance a thin
or thick film structure deposited on the surface of the suspension
arm. Varying the elastic properties of such a layer, which
especially can change the spring constant in dependence of
temperature, causes a variation of the bending of the suspension
arm and therefore a variation of the flying height of the
read/write head.
According to another embodiment, the variation of elastic
properties can also be realized by using a bulk material or layer
for the suspension arm or an according additional layer with a
magnetoelastic effect where the spring constant of the material
depends on the magnetization. The magnetization can be controlled
by an external as well as by an internal applied magnetic field
acting upon the magnetosensitive layer. An internal magnetic field
source can be realized by a second e.g. hard magnetic layer
deposited beneath or on top or close to the magnetosensitive
material or by adding a small loop as inductive element to generate
a magnetic field. Such a magnetic layer can be also used to bias or
linearize the effect. Using a magnetoelastic layer or material has
the advantage that there is not needed a continuous power
consumption in the storage device since the magnetoelastic effect
is a quasi-static effect.
It is noteworthy that the described concepts can be carried out
individually for each slider/hard disk combination and do not
depend on the peculiarities of the underlying disk storage device.
Beyond that the concepts are not limited to magnetic hard disk
storage devices and can also advantageously be applied to other
present and future spinning disks based storage devices like
optical disks etc.
Accordingly, it is an object of the invention to provide a method
and apparatus for controlling the flying height of a read/write
head above a moving storage medium, like a rotating magnetic hard
disk or a tape of a tape recording device, which allow for an
active and/or dynamic flying height adjustment or, particularly in
case of a tape recording device, adjustment of the bearing pressure
of its read/write head.
It is another object to provide a method and apparatus to allow for
precisely setting the flying height of individual storage devices,
in particular hard disk drives, at a defined value in order to meet
fabrication tolerances.
It is another object to provide a method and apparatus which allow
to compensate pressure changes in a hard disk drive and/or
contamination of an air bearing surface in a hard disk drive or a
tape storage device.
It is yet another object of the invention to provide a method and
apparatus for controlling roll, pitch and twist of a read/write
head above a rotating magnetic hard disk or above a moving tape of
a tape store which allow for an active alignment or adjustment of
these properties.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described in more detail by way
of embodiments and making reference to the accompanying
drawings.
FIG. 1 is a perspective view of a suspension arm according to the
prior art;
FIG. 2 is a schematic view of a suspension arm for illustrating the
air cushion mechanism underlying the present invention;
FIGS. 3a-3d are schematic views of different embodiments of the
present invention;
FIGS. 4a-4c are schematic views to illustrate definition of roll,
pitch and twist;
FIGS. 5a-5d are schematic views of different embodiments of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, there is shown a suspension arm 100 which is disclosed
in U.S. Pat. No. 5,377,058 and which comprises a floating
suspension 110 and a read/write head 120 according to the prior
art. The read/write head 120 is mounted on a slider 125. Electrical
supply of the head 120 including one or more signal lines is
accomplished via electrical wires 160. On its opposite side, the
suspension arm 100 is mounted on an engine flange of a hard disk
drive (not shown here) by means of a mounting flange 130.
A piezoelectric film 140 is bonded to the suspension arm 100. A
flying height correction voltage is applied to the film 140 through
electrical wires 150. Applying the correction voltage, the film 140
expands in the plain of the suspension arm 100 and due to the
adhesion between the film 140 and the suspension arm 100 introduces
a bending force to the arm 100 which forces the arm 100 to bend
along its longitudinal axis and its lateral axis.
The bending of the suspension arm 100 towards a (not shown) disk
surface increases the spring force pushing against the aerodynamic
lift acting upon the read/write head 120 or the slider 125,
respectively, so that the head 120 flies closer to the disk
surface. Thus the flying height is adjusted by the correction
voltage.
FIG. 2 is a schematic side view of a suspension arm with a slider
sliding above a disk surface of a magnetic hard disk. While the
magnetic hard disk is rotating, an air cushion disposed under the
slider exerts a force away or towards the hard disk. In equilibrium
of the force F.sub.a and the spring force F.sub.s, the head is
flying above the rotating hard disk at a balanced flying height
(FH).
According to the invention, the suspension arm comprises a material
or alternatively a layer deposited on the surface of the suspension
arm, where the spring constant strongly varies with a physical
property of the material like its temperature or a magnetic flux
through it or an applied electrical voltage. The spring force
F.sub.s, in a first approximation, can be written as F.sub.s
=k.times.1, where k is the spring constant of the material and 1 is
the longitudinal or lateral deflection of the suspension arm.
According to the invention, the spring force F is varied by
changing the spring constant k. A variation Dk hereby causes a
variation of the deflection D1 with F=const. in a first
approximation.
Referring now to FIG. 2, a view depicting a head slider assembly
200 particularly comprising a slider 210 located at a distance to a
hard disk surface 220 is shown in order to illustrate the air
cushion concept underlying the present invention. The flying height
(FH) in the following will be defined as the minimum distance
between the slider and the disk surface 220. The spatial
orientation and the bending shape of the slider 210 relative to the
disk surface can be characterized by the pitch angle a and the
crown value 230. Due to the relative movement between the disk
surface 220 and the slider 210, determined by the spinning
direction of the hard disk depicted by arrow 240, a specific air
stream 250 is formed which, according to the pitch a, results in a
force due to the aircushion at the air bearing surface 260
comprising the minimum distance FH to the disk surface 220.
The flying height (FH) of the slider 210 or the head, respectively,
is totally determined by the aforedescribed flying characteristics,
i.e. the lift and sink forces produced by the slider aerodynamics,
and the spring force with which the suspension arm 280 pushes the
slider 210 to the disk surface 260.
The following FIGS. 3a-3c depict different embodiments of a
suspension arm according to the invention.
Now referring to FIG. 3a, a first embodiment comprises a suspension
arm 300 including a or consisting of a bulk material with a spring
constant with a relatively large gradient of the elastic modulus DE
versus DT, where DT is the bulk temperature of the suspension arm
300. The suspension arm 300 is comprised of an elastic portion 310
with a thickness d.sub.1 and a rigid portion 320 with a thickness
d.sub.2. At the free end of the suspension arm 300, a slider 325 is
mounted on the suspension arm 300, 310 by means of a glue 327. The
bottom surface of the slider 325 has a distance FH to a top surface
of a hard disk 329.
The suspension arm 300 particularly comprises a heating element 330
disposed at a particular elasto-sensitive portion 340 of the bulk
material which is highlighted by cross lines and which comprises an
elevated gradient of the elastic modulus.
The heating element 330, in the present embodiment, is implemented
as a resistance wire being wound around the suspension arm.
Alternatively, the heating element 330 can be realized as a thin or
a thick layer of an electric resistance material deposited onto one
or both surfaces along the portion 340. An electric current I.sub.c
flowing through electrical supply wires 350 causes the temperature
of the elasto-sensitive material 340 to rise and therefore the
spring constant of the material 340 to decrease.
Together with a constant force F.sub.a resulting from the air
cushion effect underneath the slider 325 (see FIG. 2), the bending
curvature of the suspension arm 300 will also decrease thus
increasing the flying height FH of the slider 325 above the disk
surface 329.
Another embodiment of the invention depicted in FIG. 3b comprises,
instead of a bulk material, an elasto-sensitive layer 400 deposited
on a suspension arm 410 and comprising a thickness d.sub.layer.
Depending on the difference between the thicknesses d.sub.layer and
d.sub.bulk, a change of the spring constant of the layer 400 will
also cause a change in the bending curvature of the suspension arm
410.
This embodiment also comprises a heating element 420 which, in the
present embodiment, is implemented as a meander-shaped resistance
wire 420. An electrical current supplied by supply wires 430 and
flowing through the resistance wire 420 causes heating primarily of
the layer 400 and thus causes a change of the spring constant of
the layer 400, accordingly. This will also cause a change in the
bending curvature of the suspension arm 410 due to the so-called
"passive bimetallic effect," i.e. the decrease of the bending
momentum of the layer 400 acting upon the suspension arm 410. In
this arrangement, the actuation owing to the bimetallic effect and
the elastic effect may have opposite signs. Materials can be chosen
which show a zero actuation by varying the temperature.
Alternatively, materials with a high elastic effect can be chosen
which overcompensate the bimetallic actuation.
It is emphasized hereby that the direction of change of the bending
curve and thus the flying height depends on the sign of the
internal stress of the two-layer system and thus can be an increase
or decrease of the flying height when raising the temperature.
FIG. 3c shows an embodiment where a layer 500 of a magnetoelastic
material is deposited on a suspension arm 510. A change of the
elastic modulus of the layer 500 is induced by means of a magnetic
field which is generated by means of a wire wound in the form of a
flat coil on top of the layer 500 or around the suspension. The
coil wire 520 is supplied via supply wires 530.
FIG. 3d shows an embodiment where a hard magnetic layer (HL) is
placed on top or very close or on the close proximity to a
magnetoelastic portion of the suspension. The magnetization of the
hard magnetic layer defines the direction of magnetization of the
magnetoelastic portion of the suspension, and therefore its elastic
properties. The magnetization of HL can be switched by an
externally applied field, even a field applied outside the HDD, or
set by a short current pulse through a small inductive element
disposed on top of the HL. After the external applied field or the
current pulse, the magnetization in the HL rotates in a desired
direction and therefore defines the elastic properties of 500. The
embodiment can be designed by only using a magnetoelastic portion
which, in itself, is a hard magnetic material.
FIG. 4a is a schematic view along longitudinal axis to the rear of
a top slider 620 and a bottom slider 640 sliding above a disk
surface of a magnetic hard disk 600. While the magnetic hard disk
is rotating, an air cushion disposed under the slider exerts a
force away or towards the hard disk. As sketched, sliders 620, 640
may be parallel (zero roll) or angled with respect to the disk
surface.
FIG. 4b is a schematic side view of a top slider 620 and a bottom
slider 640 sliding above a disk surface of a magnetic hard disk
600. While the magnetic hard disk is rotating, an air cushion
disposed under the slider exerts a force away or towards the hard
disk. As sketched, the ABS of sliders 620, 640 may be parallel (0
pitch) or angled with respect to the disk surface.
FIG. 4c is a schematic side view of a bottom slider 640 sliding
above a disk surface of a magnetic hard disk 600. As sketched, the
slider may be twisted along longitudinal axis.
In FIG. 5a from German patent application DE 19603192 A1, FIG. 6, a
front part of a suspension arm 21a with slider 24 is depicted. The
suspension arm is modified by U-shaped slits 31 and 32 near the
slider 24 and straight slits 33 and 34. This way, a H-like head
mounting region is formed, with bridges 36, 38, and 39 forming a
kardanic-like suspension system. This suspension system suffers
from being non-ideal kardanic. Forces required to bend or twist the
bridges prevent the head to align the slider correctly to the disk
surface by means of air cushion pressure only, if slider was
mounted non ideal.
FIG. 5b shows a modification of the system of FIG. 5a with bridges
710 and 720 or parts of the bridges 730,740,750,760 comprised by a
material or alternatively a layer deposited on the surface of the
bridge, where the spring constant strongly varies with a physical
property of the material like its temperature or a magnetic flux
through it as already described for the suspension arm. By
selectively changing the spring constant of bridges, mounting
tolerances of the slider can be corrected to adjust roll, pitch or
twist.
FIG. 5c shows a different embodiment of the invention using another
kardanic like suspension system, comprised from crossed bridges 710
and 720. Systems depicted in FIGS. 5a to 5c, suffer from bridges
coupled to each other. Thus an individual adaption of roll and
pitch can not be maintained.
FIG. 5d shows a suspension system with decoupled axis. Bridges
710a, 710b and 720 or parts 770,780,790 of the bridges are
comprised by a material or alternatively a layer deposited on the
surface of the bridge, where the spring constant strongly varies
with a physical property of the material.
While the invention has been shown or described in only some of its
forms, it should be apparent to those skilled in the art that it is
not so limited, but is susceptible to various changes without
departing from the scope of the invention.
* * * * *